The present invention relates generally to medical diagnostics and, in particular, to apparatus for measuring length and other physical characteristics of arteries, veins, and other lumens of the body.
In the field of medical diagnostics and treatment, cardiologists often treat patients with conditions affecting blood flow in vessels near the heart. In these treatment procedures, various measurements of affected blood vessels need to be accurately determined. In an effort to restore blood flow through cardiac arteries narrowed by plaque deposits or other obstructions, interventional procedures such as balloon catherization, are often used. In this particular procedure, an inflatable balloon is fed into the cardiac artery and inflated to dilate the artery in the affected length of the vessel. After dilation, a stent, which is a thin scaffold or support typically made of plastic or metal and formed in the shape of a perforated tube, is delivered and installed within the blood vessel to maintain an increased blood flow through the cross-sectional flow path.
One of the difficulties cardiologists encounter in this procedure is the measurement of the distance and diameter of the affected length. These measurements are critical, because they are used to determine the stent size appropriate for the length. Accurate sizing of the stent is important to ensure its proper functioning. Consequently, selecting the appropriate stent is critical to the success of the procedure. The prior art contains several methods and apparatuses for making this measurement.
In one prior art approach, a cardiologist reviews x-ray images of the heart after contrast material is introduced into the bloodstream of the patient. The cardiologist must rely on experience and training to make a judgment regarding the size of the affected length. As such, this method may not always provide repeatability and precision in the measurement of the length.
In another prior art approach, x-ray images are processed by computer image analysis systems, which estimates the dimensions of the affected length. These measurements are based on various assumptions about the position of the artery, the axis of the x-ray image, etc. Also, the additional equipment required for this procedure may make it economically unfavorable or even cost-prohibitive. A further prior art approach uses ultrasonic transducers that are fed into the patient""s arteries via a catheter which xe2x80x9cimagesxe2x80x9d the vessel walls to estimate the length. This device is also very expensive and cumbersome to use.
In view of the foregoing, there is a need in the art to provide a new, simple device capable of accurately measuring the dimensions of a length, within a blood vessel, such as a cardiac artery.
The present invention is directed to devices for measuring length and/or diameter in arteries, veins, and other lumens of the body. In a length-measuring embodiment, the apparatus includes a hand-held unit which remains outside the body, but which couples to, and cooperates with, one or more invasive catheters and/or guidewires to measure a length within a vessel. The hand-held unit further includes an inner barrel and outer barrel that slide relative to one another to position a scale with markings indicative of the length. The preferred embodiment also includes a zero ring for initializing the relative position of the barrels and scale in conjunction with the onset of the length measurement to ensure the accuracy of a measurement. The apparatus optionally includes a feature to hold a guidewire in a stationary position.
As is typical in the surgical profession, a radio opaque marker or similar device is placed on the catheter tip or other distal point. The marker point is then positioned at one end of the lesion, and subsequently displaced to the opposite end of the lesion using the inventive device. The measurement of a lesion, plaque region, obstruction, or other length of interest may be made by using the device according to the present invention.
One advantage of the invention is that the device may be used to measure the distance between any two points in the blood vessel. Another advantage is that the device may be used for measurement in any vessel that it or an attached catheter and/or guidewire can be inserted into and that fluoroscopy can view. A further advantage of the present invention is that the apparatus is used in a variety of manners to determine the dimensions of a length of the blood vessel.
A device for measuring the inside diameter of a vessel according to the invention includes a tube, measuring wires, and a knob. The tube is as long as necessary to reach the desired location, yet flexible enough to maneuver through vasculature. Holes run the length of the tube to accommodate multiple lumens including a central lumen that runs the entire length of the tube and a plurality of other lumens which are uniformly spaced around the central lumen but stop a short distance from the tip of the tube. These other lumens also have a slot cut into them that exposes a portion of the lumen. Wires are inserted in all the lumens except the central lumen. When the wires are pushed on their proximal ends, they expand by bulging out of the slots into the respective lumens. When the wires make contact with the inside of the vessel, they indicate the inside diameter of that vessel.